Characterization of the Protective Properties of Hydrotalcite on Hybrid Organic-Inorganic Sol-Gel Coatings

The effect of hydrotalcite (HT) on the protection of aluminum alloy by sol-gel films was investigated by electrochemical impedance spectroscopy (EIS) and electrochemical noise measurements (ENM). Samples of 1, 5, and 10 wt% of HT were tested. Improved performance was observed and the main action of HT was explained by its buffering capacity, which reduces locally aggressive conditions and maintains the stability of the films. A comparison between EIS and ENM results showed differences in the response of the coatings that may have come from pitting activation triggered by EIS measurements at the beginning of immersion, which, in turn, may lead to premature failure and erroneous coating evaluation.